San Diego County housing prices rebounded last month after dropping unexpectedly in January, but experts said they are waiting for spring sales to tell them whether the market is improving or just treading water.

MDA DataQuick reported yesterday that the county’s median price in February rose $17,000 from the previous month to $322,000, its level for most of the second half of 2009. On a year-over-year basis, the median was up 13 percent, the best increase in five years.

DataQuick analyst Andrew LePage said the increase was not caused by a sudden increase in appreciation but by a change in the market mix. The homes that closed escrow in February were in all price ranges, he said, instead of mostly low-cost distressed properties.

“What did sell in January tended to be more concentrated in (homes for) the first-time buyers and investors,” LePage said, which caused the median to fall from $330,000 in December to $305,000 in January.

But if February saw a more normal distribution of sales, it also was the third straight month that sales of foreclosed homes rose. In February, foreclosures represented 38.8 percent of resales, compared with 38.2 percent in January and 35.8 percent in December.

“We’re still playing cleanup with a lot of properties that entered the foreclosure process last year,” LePage said.

Robert Brown, an economics professor at California State University San Marcos, said he has been using the word “stability” to describe the local housing market, because prices seemed to have bottomed out last year and have risen gradually in different neighborhoods. The county’s median peaked at $517,500 in November 2005 and fell to a low of $280,000 in January 2009. It is now 15 percent above the bottom and 37.8 percent below the peak.

“In terms of having a big rebound, I don’t foresee that, but we have to wait a couple of months before we see what we’re talking about,” Brown said.

He said there are too many unknowns with the economy to predict the rest of the year, citing a possible rise in interest rates and the health care legislation pending in Congress.

And then there’s the “shadow inventory” of homes that banks have repossessed but not yet listed for sale, as well those that could be foreclosed if owners cannot get loans modified or short-sales approved. A short-sale is a home that is sold for less than its outstanding mortgage balance.

“We’re not really going to have a stabilized market until that inventory runs through the system,” Brown said.

Trans-Union, a credit and information management company, reported that 10 percent of San Diego mortgages were at least two months delinquent at the end of last year — a figure that in the past has typically pointed to foreclosure.